A cosine function is given in the form:
[tex]y=A\cos(x-h)+k[/tex]
where |A| is the amplitude, h is the horizontal shift (also called a phase shift) and k is the vertical shift.
The function is given to be:
[tex]\begin{gathered} y=8\cos(\frac{1}{4}x) \\ A=8 \end{gathered}[/tex]
Therefore, the amplitude is 8.
